This invention relates to a neck finish on a container having an anti-thread distortion feature and more particularly relates to a neck finish for a container having a clearance designed into a bottle thread to allow horizontal withdrawal of bottle thread molding surfaces during manufacture.
Currently, in the forming of containers of plastic, glass, or other known materials, an extruded parison or injection molded preform is initially formed. In the use of plastics, materials such as polyethylene terephthalate (PET) or High Density Polyethylene (HDPE) are most commonly found. In the blow molding process for a container, the preform is positioned within a mold cavity which is defined by the coming together of two mold halves and the preform is held in place by the neck finish between the mold halves. In the molding process the preform is longitudinally stretched, usually by a push rod, and then laterally expanded by injection of a blowing gas or fluid into the interior of the preform. Upon completion of the molding process the mold halves are moved apart horizontally and in many instances during the separation of the mold surface, and particularly in the neck finish, the molding surfaces pull, tear, or rip the helically-shaped formed bottle container neck threads. A common problem found in the forming of containers utilizing steep-pitch threads is distortion of the threads upon removal of the container from the mold.
It is an object of the present invention to provide a neck finish for a bottle container including an anti-thread distortion feature.
It is another object of the present invention to provide a neck finish for a container which includes a clearance designed into a bottle thread to allow horizontal withdrawal of the bottle thread molding surfaces during the molding operation of a container without pulling, tearing, ripping, or otherwise deforming threads on the neck of the container.
It is yet another object of the present invention to provide a neck finish for a container which allows for the use of steep-pitch threads.
In accordance with the present invention, a blow molded container is formed from a parison. The neck finish of the container has been modified to assist in the separation of the mold upon the completion of the formation of a container without deforming the container thread profile. The neck finish is provided with a pair of recesses on opposed sides of the neck and also of the mold, each recess being disposed within a thread of the neck and in alignment with the direction of movement of the axially moveable mold sections which make up the container forming mold.
More particularly, the present invention provides a container with a neck portion having a first open end and an opposed second end opening into a body portion of the container. A helical thread of the type such as a steep-pitch helical thread or the like encircles the neck. The helical thread is provided for engagement with mating threads of a closure or container cap. A pair of recesses are provided within the helical thread wherein the recesses are spaced 180xc2x0 apart. The recesses are formed by fingers in at least two axially movable mold sections. When the mold sections are joined together they form a mold cavity from which the container is formed.